Generally described, computing devices and communication networks can be utilized to exchange information. In a common application, a computing device can request content from another computing device via the communication network. For example, a user at a personal computing device can utilize a software browser application to request a network resource, such as a Web page, from a server computing device via the Internet. In such embodiments, the user computing device can be referred to as a client computing device and the server computing device can be referred to as a content provider.
Content providers are generally motivated to provide requested content to client computing devices via efficient transmission of the content. Users are generally interested in receiving content or having content rendered promptly. Some content providers attempt to facilitate the delivery of requested content, such as Web pages or resources identified in Web pages, through a network computing provider that caches frequently accessed content or resources.